System and method for power oscillation damping in a power generating system

A method for controlling an inverter-based generator to damp power system oscillations, wherein the inverter-based generator is in a plant that is connected to a grid at a point of intersection (POI), the method comprising:

• at a local controller configured with the inverter-based generator, generating an auxiliary signal from one or more grid signals having a characteristic indicative of a power system oscillation;
• at the local controller, generating a reactive power command signal that is separate from the auxiliary signal and indicates a desired reactive power output from the inverter-based generator;
• and
• at the local controller, using the auxiliary signal to modulate reactive power output from the inverter-based generator from that indicated by the reactive power command signal to improve damping of the power system oscillations.

A method for controlling an inverter-based generator to damp power system oscillations, wherein the inverter-based generator is in a plant that is connected to a grid at a point of intersection (POI), the method comprising:

• at a plant controller configured with the inverter-based generator, generating an auxiliary signal, wherein the auxiliary signal is generated from one or more grid signals having a characteristic indicative of a power system oscillation;
• at the plant controller, using the auxiliary signal to modify a reactive power command going to a local controller configured with the inverter-based generator to improve damping of the power system oscillations;
• wherein the generating of the auxiliary signal at the plant-level controller further comprises the plant level controller receiving capability limits at operating conditions of each of the inverter-based generators and adjusting the auxiliary signal to limit a change in reactive power (ΔQ) utilized for damping, wherein the limit is calculated and implemented at the plant level as a percentage of the reactive power capability of the plant or inverter-based generators;
• and
• further comprising utilizing a switchable washout filter having at least two washout filters with different time constants upstream of a (ΔQ) limiter, wherein when the (ΔQ) limit is reached, output from the switchable washout filter is changed to the washout filter having a lower time constant.

A system for controlling a wind farm to dampen power system oscillations on an electrical grid, the wind farm having a plurality of wind turbines electrically connected to the electrical grid at a point of interconnection (POI), the system comprising:

• a generator and associated wind turbine controller configured with each of the wind turbines, the wind turbine controllers comprising a processor for implementing a plurality of first operations;
• a farm-level controller communicatively coupled to each of the wind turbine controllers, the farm-level controller comprising a processor for implementing a plurality of second operations, the plurality of second operations comprising:
• receiving one or more grid signals having a characteristic indicative of a power system oscillation;
• generating an auxiliary signal from the grid signals;
• transmitting the auxiliary signal to the wind turbine controllers;
• the plurality of first operations at the wind turbine controllers comprising:
• receiving a reactive power command signal at the wind turbine controller that is separate from the auxiliary signal and indicates a desired reactive power output from the wind turbine generator;
• and
• using the auxiliary signal to modulate reactive power output from the wind turbine generator from that indicated by the reactive power command to change a voltage at the POI, the voltage change damping the power system oscillations.

A system for controlling a wind farm to dampen power system oscillations on an electrical grid, the wind farm having a plurality of wind turbines electrically connected to the electrical grid at a point of interconnection (POI), the system comprising:

• a generator and associated wind turbine controller configured with each of the wind turbines, the wind turbine controllers comprising a processor for implementing a plurality of first operations;
• a farm-level controller communicatively coupled to each of the wind turbine controllers;
• the plurality of first operations comprising:
• receiving one or more grid signals having a characteristic indicative of a power system oscillation;
• generating an auxiliary signal from the grid signals;
• generating a reactive power command signal that is separate from the auxiliary signal and indicates a desired reactive power output from the wind turbine generator;
• and
• using the auxiliary signal to modulate reactive power output from the wind turbine generator from that indicated by the reactive power command signal to change a voltage at the POI, the voltage change damping the power system oscillations.

A system for controlling a wind farm to dampen power system oscillations on an electrical grid;

• the wind farm having a plurality of wind turbines electrically connected to the electrical grid at a point of interconnection (POI);
• the system comprising:
• a generator and associated wind turbine controller configured with each of the wind turbines;
• a farm-level controller communicatively coupled to each of the wind turbine controllers, the farm-level controller comprising a processor for implement a plurality of first operations;
• the plurality of first operations comprising:
• receiving one or more grid signals having a characteristic indicative of a power system oscillation;
• generating an auxiliary signal from the grid signals;
• using the auxiliary signal to modify a reactive power command transmitted to the wind turbine controllers to modulate reactive power output from the wind turbine generator to change a voltage at the POI, the voltage change damping the power system oscillations;
• wherein the generating of the auxiliary signal at the farm-level controller further comprises the farm-level controller receiving capability limits at operating conditions of each of the inverter-based generators and adjusting the auxiliary signal to limit a change in reactive power (ΔQ) utilized for damping, wherein the limit is calculated and implemented at the plant level as a percentage of the reactive power capability of the plant or inverter-based generators;
• and
• further comprising utilizing a switchable washout filter having at least two washout filters with different time constants upstream of a (ΔQ) limiter, wherein when the (ΔQ) limit is reached, output from the switchable washout filter is changed to the washout filter having a lower time constant.

A method for damping power system oscillations in a power system network having one or more local inverter-based generators within a plant, the plant connected to a grid at a point of intersection (POI), the method comprising:

• at a plant-level controller, receiving one or more grid signals having a characteristic indicative of a power system oscillation;
• at the plant-level controller, generating an auxiliary signal from the grid signals;
• transmitting the auxiliary signal to a local controller of one or more of the inverter-based generators;
• at the local controller, using the auxiliary signal to modulate reactive power output from the inverter-based generators to improve damping of the power system oscillations;
• wherein the grid signals are any one or combination of:
• an active or reactive power flow in one or more grid transmission lines, a current magnitude in one or more grid transmission lines, a voltage magnitude or angle at the POI, a voltage magnitude or angle at a remote bus, or a grid frequency;
• and
• wherein a plurality of the grid signals are received at the plant-level controller, the auxiliary signal generated from a weighted combination of the plurality of the grid signals.

A method for damping power system oscillations in a power system network having one or more local inverter-based generators within a plant, the plant connected to a grid at a point of intersection (POI), the method comprising:

• at a plant-level controller, receiving one or more grid signals having a characteristic indicative of a power system oscillation;
• at the plant-level controller, generating an auxiliary signal from the grid signals;
• transmitting the auxiliary signal to a local controller of one or more of the inverter-based generators;
• at the local controller, using the auxiliary signal to modulate reactive power output from the inverter-based generators to improve damping of the power system oscillations;
• wherein the generating of the auxiliary signal at, the plant-level controller further comprises the plant level controller receiving capability limits at operating conditions of each of the inverter-based generators and adjusting the auxiliary signal to limit a change in reactive power (ΔQ) utilized for damping, wherein the limit is calculated and implemented at the plant level or at each of the inverter-based generators as a percentage of the reactive power capability of the plant or inverter-based generators;
• and
• further comprising utilizing a switchable washout filter having at least two washout filters with different time constants upstream of a (ΔQ) limiter, wherein when the (ΔQ) limit is reached, output from the switchable washout filter is changed to the washout filter having a lower time constant.